This is a reference entry from MDN Web Docs. A full explanation with fixes has not been written yet.
SyntaxError: Octal literals are not allowed in strict mode. (V8-based)
SyntaxError: Decimals with leading zeros are not allowed in strict mode. (V8-based)
SyntaxError: Unexpected number (V8-based)
SyntaxError: "0"-prefixed octal literals are deprecated; use the "0o" prefix instead (Firefox)
SyntaxError: Decimal integer literals with a leading zero are forbidden in strict mode (Safari)
- Category
- SyntaxError in strict mode only
- Severity
- error
- Runtime
- both
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Source: MDN Web Docs. Data fetched 2026-09-25T01:48:37.273Z.